In the area of wound repair and clinical wound management, a quantitative method for assessing wound healing is necessary or at least extremely desirable. The cost of treating wounds, particularly chronic, non-healing wounds is quite large, in terms of health care costs as well as pain and suffering of the patient under these circumstances. As the number of individuals suffering from non-healing wounds will most likely increase due to the increasing general age of the population as well as increase in life expectancy, there has been found a need to assess wound healing in vivo, for which various methods and techniques have been utilized. In vivo assessment of wound repair has developed using various methodologies, including both subjective and objective methods, and superficial methods or more detailed wound assessment which attempts to quantitatively analyze wound healing.
Superficial wound assessment may be performed by subjective or objective tests, including analysis of pain, erythema, induration, and edema, these subjective assessments being of no particular help in quantitatively measuring and evaluating wound healing. Objective methods which do allow some quantitative assessment of wound repair include direct measurement of wound size, wound mapping, wound photography, and volumetric measurement of wounds. For more detailed wound assessment and quantitative measurements, various approaches have been adopted, which include invasive and non-invasive techniques. Invasive assessment of wound healing may be performed by biochemical analysis of wound fluids and/or tissue and can give valuable information particularly with regard to the inflammatory stage of wound healing. Histological evaluation of wound tissue has also provided information on the structure and components of the wound, and has supported a significant role for macrophages in the control and stimulation of wound repair. Another invasive technique includes monitoring of granulation tissue formation on the wound, indicating the influx of macrophages, fibroblasts, and neovasculature into the wound. Invasive techniques to monitor granulation tissue formation have been developed for various aspects of this formation. Additionally, blood perfusion in a wound may be correlated to the angiogenic response of the wound, and techniques such as angiography after an injection of a suitable dye, electronmicroscopy and histological or immunohistochemical techniques have been developed in this regard. Finally, matrix formation and the accumulation of collagen in the wound is a final portion of the wound reparative process, and measurement of tensile strength of the wound or biochemical methods of analysis of the wound may be used.
As should be recognized, such invasive techniques are not extremely desirable for human patients, and do not allow repeated, reproducible measurements of a single wound while not interfering with the healing process. These methods do not allow time course studies of a wound to assess treatment procedures or the like. Thus, non-invasive methods to evaluate wound healing have been developed so as not to induce trauma to the wound during the healing process, and allow time course studies of a wound. Several techniques for non-invasively assessing wound healing include laser doppler flowmetry, which can be utilized to measure perfusion and angiogenesis in the healing of a wound, ultrasonic pulse echo techniques yielding a two-dimensional image of the wound, transcutaneous gas monitoring to measure the levels of oxygen and carbon dioxide released from the healing tissue, stereophotogrammetry for measurement of wound volumes, video image analysis, and tensometry which non-invasively measures the tensile strength of a wound. Although each of these non-invasive methods is beneficial in that no induced trauma to the wound will occur, none gives accurate and repeatable measurements of a wound throughout the healing cycle which will allow quantitative assessment of treatment procedures used in the healing process. For example, growth factors are increasingly used in wound treatment, as well as other new treatments typically based on final wound closure. No existing quantitative methods provide reliable early indicators of wound healing without significant effort or expense resulting in lengthy clinical trials and extensive patient care with increased cost. Further, as the number of effective treatments grows, it becomes more difficult to determine the optimal therapy for a particular wound situation, particularly if no quantitative analysis or assessment tool is available. There has therefore been found a need to provide a simple, non-invasive system to detect subtle but important changes in healing tissue, particularly during early stages of wound repair.
As an alternative to the assessment of wound healing, there has also been found to be a need to accurately measure surface profiles and textures in a variety of applications. For example, such measurements are desirable in plastic surgery or other surgical reconstructions or treatment of hypertrophic scarring, and yet no means for quantitative analysis is generally available. Apart from medical use, any industrial process which requires monitoring of surface texture and profile may benefit from a quantitative measurement tool which is accurate and cost effective in its operation. Non-invasive three-dimensional measurement of surface profile, volume and analysis of surface texture is therefore desirable in a variety of medical and industrial applications, and there therefore is a distinct need for a method and apparatus for such analysis.